SAN BERNARDINO, Calif. >> California’s newest huge wildfire advanced on thousands of homes Wednesday, feeding on drought-stricken vegetation and destroying an untold number of structures as it expanded to nearly 47 square miles.

Flames climbed the flanks of the San Gabriel Mountains toward the town of Wrightwood, where authorities said that only half of the community’s 4,500 residents had complied with evacuation orders.

Officials estimated that more than 34,000 homes and some 82,000 people were under evacuation warnings.

Less than 24 hours after the blaze began 60 miles east of Los Angeles, the fire command assembled a fleet of 10 air tankers, 15 helicopters and an army of 1,300 firefighters, many of them just off the lines of a wildfire that burned for 10 days just to the east.

At a dawn briefing, half the firefighters raised their hands when an official asked how many had just come from the earlier blaze, part of a siege of wildland infernos up and down California this year.

Countless big rigs were parked on both sides of the pass, waiting for Interstate 15 and a web of other roads to reopen. Alternate routes involved significant detours. The pass is a major route for travel from the Los Angeles region to Las Vegas and also carries significant daily commuter traffic for high desert residents.

The speed of the fire’s spread astonished those in its path.

“This moved so fast,” said Darren Dalton, 51, who along with his wife and son had to get out of his house in Wrightwood. “It went from ‘Have you heard there’s a fire?’ to ‘mandatory evacuation’ before you could take it all in. This is a tight little community up here. Always in rally mode. Suddenly it’s a ghost town.”

Hundreds of cars packed with belongings and animals left the town. The air for miles around the blaze was filled with smoke. The sound of explosions — possibly from ammunition stored in homes — could be heard in the distance.

The fire erupted in a landscape ready to burn after years of drought. The weather at the time was hot, dry and windy — conditions not expected to begin easing until late Thursday or Friday.

Devouring ranchlands, the blaze surged west to the Los Angeles County line and north to the Mojave Desert.

Eric Sherwin of the San Bernardino County Fire Department confirmed Tuesday night that the flames had burned at least a dozen buildings, some of them homes. He said he had seen all kinds of things burn, including the Summit Inn, a historic diner near I-15.

The blaze was among several large fires burning up and down California, from Shasta County in the far north to Camp Pendleton Marine base in San Diego County. It came after several steady weeks of major fires around the state, even though the full force of the traditional fire season has yet to arrive.

Gov. Jerry Brown declared a state of emergency in the area within hours of the latest fire breaking out, a move that more often comes after a blaze has done several days of destruction.

Six firefighters were briefly trapped by flames at a home where the occupants had refused to leave, forcing the crew to protect the house, fire officials said.

“We were fully engulfed in smoke,” firefighter Cody Anderson told KCBS-TV. “It was really hard just to see your hand in front of your face.”

“We just hunkered down and sat there and waited for the fire to blow over,” he said.

Anderson and another firefighter were treated for minor injuries.

As that fire surged, a major blaze north of San Francisco was fading, and about 4,000 people in the town of Clearlake were allowed to return home.

Their relief, however, was tempered with anger at a man who authorities believe set the blaze that wiped out several blocks of a small town over the weekend along with 16 smaller fires dating back to last summer.

Investigators in Northern California said Tuesday that they had been building a case against the suspected arsonist, 40-year-old construction worker Damin Anthony Pashilk, for more than a year. But they did not have enough evidence to make an arrest until the weekend blaze ripped through Lower Lake.

The fire destroyed 175 homes and other structures in the working-class town of Lower Lake.

“What I’d do to him, you don’t want to know,” said Butch Cancilla, who saw his neighbor’s home catch fire as he fled on Sunday. Cancilla still does not know the fate of his own home.

“A lot of people want to hang him high,” his wife, Jennie, added.

An attorney listed as representing Pashilk did not return a call requesting comment. Pashilk is scheduled to be arraigned Wednesday.